Myosin VI is involved in the structural organization and molecular composition of epididymal epithelial cells in mouse†

Myosin VI (MYO6) is the only actin-based motor protein that moves toward the minus end of actin filaments. It participates in multiple cellular processes, including endocytosis, secretion, autophagy, and the formation of apical stereocilia and microvilli in highly specialized epithelia. These diverse functions are mediated by specific cargo-adaptor proteins that recruit MYO6 to distinct cellular compartments. We have previously demonstrated that loss of MYO6 function in Snell's waltzer mice leads to several defects during spermatogenesis, resulting in reduced male fertility. Here, we show for the first time that MYO6 and selected binding partners are differentially expressed in mouse epididymal epithelium, a highly specialized mammalian epithelia developing apical microvilli. Using immunocytochemistry, confocal microscopy, and biochemical approaches we found that: (i) MYO6 is present in the epithelium of the common efferent duct and all segments of the epididymis, (ii) MYO6 and Dab2 colocalize predominantly at the apical surface of epithelial cells in the efferent duct and caput, (iii) MYO6 and GIPC1 are mainly detected in epithelial cells in the caput and corpus, with the lowest level observed in the cauda. Moreover, depletion of MYO6 results in altered distribution of clathrin and APPL1 in epididymal epithelial cells and causes ultrastructural abnormalities. Altogether, our findings indicate that MYO6 contributes to the endocytic pathway in the mouse epididymal epithelium, a process essential for generating the microenvironment required for sperm maturation. In addition, MYO6 supports the structural organization of apical microvilli, thereby facilitating sperm transport through the epididymal duct.